Devices of this type have already been disclosed, for example in patent U.S. Pat. No. 6,220,909 B1. That document describes an avalanche airbag inflation device intended to operate notably using a cartridge of nitrogen compressed to 200 bar. The cartridge is assembled with a control mechanism that allows the gas to be released in response to a user action. The gas, once released following the piercing of the cartridge, is conveyed to two inflation mechanisms, by pipes, each inflation mechanism being associated with an inflatable bag.
The gas is injected into a cylindrical air intake chamber provided in each of the inflation mechanisms by an injection nozzle arranged substantially in line with the central axis of the air intake chamber. This chamber comprises a plurality of openings in its lateral wall so that atmospheric air can be sucked in in response to the injection of the high-pressure gas. The air sucked in is accelerated by a Venturi effect to inflate the corresponding inflatable bag quickly with a sufficient volume, by applying a multiplication factor (volume of air/volume of compressed gas) to that of the volume of compressed gas available, thanks to the addition of the air.
Each of the inflation mechanisms further comprises a nonreturn check valve to prevent the corresponding inflatable bag from becoming deflated via the inlet when it is fully inflated.
As an alternative to nitrogen, it is also known practice to use compressed air as the compressed gas at high pressure.
In general, the multiplication factor applied in the known devices is not very high, of the order of 2 to 3 (which means that the volume of atmospheric air injected into the airbag is of the order of 2 to 3 times the volume that the gas represents in the airbag once it has expanded) and entails the use of a significant volume of compressed gas in order to be able to inflate the airbag.
The space occupied by the compressed-gas cartridge thus contributes significantly to the overall space occupied by the inflation device, and this is why the abovementioned US Patent proposes a design of the device that comes in modular form, which means to say that allows the various component parts of the device to be located at different parts of a pack for example.
However, in that case, getting the device into or out of a backpack, for example, is a complicated matter because each of its component parts has its own means of attachment that have to be done up or undone.
It will also be noted that, aside from the requirement that has to be observed regarding the airbag inflation volume, it is absolutely essential that the airbag be inflated quickly. As a general rule, an avalanche airbag needs to be inflated in around 2 to 4 seconds.